Electromagnetic vibrator



2 Sheets-Sheet 1 Fned'nec. 29, 1949 IIYI.

INven To R 13.4. mmz' l 4T. QL; @NSA QNQN JQ.: SMV mmN, OQN d. Ill .Q IQ |.|l|.|| l l -l l r||. Y WIWI MN AN fr@ WH,... Hw MMIJIIH Q @1 www 1Q Q w @i NN *uw June 9, 1953 n. A. STEWART ELECTROMAGNETIC vIBRA'roR 2 Sheets-Sheet 2 Filed Dec. 29 1949 Patented June 9, 1953 ELECTROMAGNETIC VIBRATOR Donald Arnott Stewart, Hammersmith, London, England, assignor to Westool Limited, St. Helens Auckland, England, a British company Application December 29, 1949, Serial No. 135,611 In Great Britain January 17, 1949 2 Claims. 1,

This invention relates to electro-magnetic vibrators and particularly to vibrators for vibrating concrete during setting, but is applicable for other purposes such as cutting stone, brickwork etc., agitating liquids for effective stirring and emulsicat'ion and for coinpacting powdered materials and carbon granules. Heretoiore, it has been yusual for one part of the electro-magnetic vibrator to be rigidly mounted in the framework carrying the article to be vibrated while the other part of the vibrator was connected directly to said article so that the framework took the greater part of the reaction.

`1 'According to the present invention a portable electro-magnetic vibrator is provided in which a part thereof to be supported yby hand has sufficient mass for its inertia to provide the required reaction for the vibrating part, which vibrating part is attachable to or engageable with the article to be vibrated.

The invention is particularly applicable where the rate of vibration is of the order of 3,000 to 12,000 vibrations per minute.

It is found that the ratio of the masses of the main body of the vibrator to its armature should not be less than 2:1.

The electro-magnetic vibrator may be energised direct from the alternating mains.

In order that the minimum power input may be absorbed the vibrating part is so spring mounted on the other part as to resonate at twice the frequency of the supply.

The following is a more detailed description of a portable vibrator for vibrating setting concrete, reference being made to the accompanying drawing in which:

Figure 1 is a part elevation and part section on the line I-I of Figure 2,

Figure 2 is as to the top left of the ngure a cross-section on the line C-C of Figure 3 and as to the top right a cross-section on the line E-E of Figure 3 and as to the bottom right a cross-section on the line F-F of Figure 3 and as to the bottom left an end elevation looking in the direction of the arrow B,

Figure 3 is a part elevation and part section in a plane at right angles to the section of Figure 1,

Figure 4 is as to the top left a cross-section on the line D-D of Figure 3 as to the top right a section on the line C-C of Figure 3, as to the bottom right a section on the line B-B of Figure 3 and as to bottom left an end elevation looking in the direction of arrow A in Figure 3.

The stator of the vibrator comprises a number of soft iron laminations which provide a central core I flanked on either side by portions I I Z of the laminations whichprovide a return flux path, and which are connected at their ends to saidcentral core. The central core is surround- `ed by an energising coil i2 for connection direct to the mains. The laminations are clamped between two plates I3, I4 by means of suitable clamping bolts I5. The two plates have secured at opposite ends heads It, Il between which an encircling casing I9 is arranged, one of said heads I'I is provided with a threaded bore I9 which accommodates a threaded sleeve 20. The sleeve is formed with an internal flange 2l intermediate to its ends. A rod 22 passes through said sleevey and its inner end is screw-threaded at 23-to receive a clamping member 24 for a 1aminated armature 25. Theclamping member is arranged to be slidably supported on bolts 26 which secure the head I'I to the aforesaid clamp.. ing plates I3, I4 of the stator. The other head I6 is secured by similar bolts 37 to the clamping plates and is provided with a handle 35. The screwed sleeve provides a means of adjusting the air gap between the armature laminations 25 and the cap l0. This adjustment may be used to vary the power delivered by the Vibrator. The rod 22 outside the sleeve is screw-threaded to receive an abutment 28 which is encircled by a cap member 29 which extends over the outside of the sleeve. A heavy helical spring 30 encircles the rod 22 and is arranged between the abutment and said internal flange 2I. A similar heavy spring 3l is arranged between the flange 2I and the aforesaid clamping member 24 for the armature. The threaded sleeve 20 is provided with a suitable lock nut 32. With this arrangement, the initial compression of the two springs 30, 3l may be adjusted mutually so as to be equal and so as to provide a natural periodicity of vibration equal to twice the frequency of the supply mains.

The outer end of the rod 22 is screw-threaded to receive a coupling 33 by means of which it may be attached to an extension 34. A flat disc (not shown) may be attached to the extension for application to the article to be vibrated or the extension may carry a tool holder.

Means may also be provided for stubbing or quickly arresting the relative movement of the part of the vibrator so as to apply a degree of shock to the material or body vbeing vibrated. This stubbing may be effected by suitably adjusting the spring retaining cap 2.. so that the abutment 28 meets the sleeve 20 carrying the spring, before the armature hits the core pole faces.

The weight of the parts 22, 25, 33 and 34 should not be more than about half the weights of the remaining parts.

I claim:

1. A portable electro-magnetic vibrator for use with an alternating supply of known frequency comprising a laminated core arranged to provide two pole faces, an energizing coil associated with said core, which core is clamped between two plates, two heads arranged at opposite ends of and secured to said two plates, a hand-grip secured to one head, the other of which heads is provided with a threaded bore, an externally threaded tubular member engaging said threaded bore and having an internal flange intermediate of its ends, a bearing at one end of said tubular member, a rod extending through said bearing, abutments on said rod on opposite sides of said flange, an armature secured to said rod and spaced a short distance from said pole faces, helical springs encircling said rod on opposite Vsides of said flange, each of which engage said flange and one of said abutments, the mass of which armature energizing coil and heads on vthe one hand, and the mass of the rod and aruse with an alternating supply of known fref quency comprising a laminated core arranged 'to providetwo pole faces, an emergency coil associated with said core, which core is clamped vbetween two plates, two heads arranged at opposite ends of and secured to said two plates, a

hand-grip secured to one head. the other of which heads is provided with a threaded bore, ail externally threaded tubular member engaging said threaded bore and having an internal flange intermediate of its ends, a bearing at one end of said tubular member, a rod extending through said bearing, abutments axially adjustable along said rod on opposite sides of said ange, an armature secured to said rod and spaced a short distance from said pole faces, helical springs encircling said rod on opposite sides of said ange, each of which springs abut the flange and one of said abutments, the mass of which armature energizing coil and heads on the one hand and the mass of the rod and armature on the other hand and the stiffness of the springs are so selected in relation to the frequency of supply that resonance is set up when the energizing coil is Number energized.

DONALD ARNOTT STEWART.

Y References cited in the me of this patent UNITED STATES PATENTS 

